Gaseous discharge device



Jan. 30, 1934. L DE lFQREST 1,944,929

GASEOUS DISCHARGE DEVICE Filed July 13, 1929 umtoz @3M f www@ da #94APatented Jan. 30, 1934 UNITED STATES PATENT OFFICE GASEOUS DISCHARGEDEVICE Application July 13, 1929. serial No. 377,937

8 Claims.

This invention relates in general to gas lled electron discharge devicesparticularly designed for photographic recording of fluctuating currentsand especially for photographic sound recording.

One of the objects of this invention is the provision of a gaseousdischarge device which has a longer life as compared with devices ofthis type now known.

Another object of this invention involves the construction of anelectron discharge device which is not subject to blackening of theglass walls of the enclosing envelope;

A still further object of this invention is the la provision of a deviceof this type so constructed that after operation for a few hours itsoperation becomes stable and the amount of light given oif under anyexcitation is practically constant.

An additional object of this invention is to provide an electrondischarge device of such construction that the cathode absorbs the gasescontained within the envelope and the materials therein to a less degreethan is now commonly experienced.

A.' still further object of the invention is to employ a cathode indevices of this type of tantalum and molybdenum.

These and other objects as will appear from the following disclosureare' secured by means of 80 the device of this invention.

This invention resides substantially in the combination, construction,arrangement, and relative location of parts, all as will be described ingreater detail hereinafter.

Referring to the drawing- Figure 1 is a longitudinal cross-sectionalview through one form of device embodying the principles of thisinvention;

Fig. 2 is an endrelevational view of the de- 40 vice; and

Fig. 3 is a sectional view of a modied form of device.

Heretofore any gaseous discharge devices Ias known when employed forsound recording purposes and the like have had a short useful life,usually of only a few hours duration. This short life is due chiefly toblackening of the glass .through which the light from the gas dischargepasses due to the deposition on the interior of the glass containingvessel of metallic particles torn ofi by the discharge from the surfaceof the electrodes or electrode. It is also due in part to the gradualabsorption of gases by the electrodes or by the insulating material inthe tube. This invention has to do with the construction of gaseousdischarge devices which avoids the aforementioned diificulties andfurnishes a discharge tube which has an indefinite life, the light fromwhich after a few hours use, attains a definite stable value and remainspractically constant.

Some of the advantages of a device of this nature, which is known in thevart as a photion, are derivedfrom the fact that a cathode made oftantalum or molybdenum is employed. Other fea- A tures which produce theadvantages of this invention lie in the fact that the cathode issurrounded by an envelope of insulating material and is so constructedthat it may be placed very close to the rounded, smooth end of the glassvessel. In addition, the end of the cathode is polished so that it actsas a mirror, thereby somewhat increasing the illuminating efficiencyofthe discharge device.

Referring to the drawing, the elements of the discharge tube areenclosed within a glass envelope 1 which is sealed off in the usualmanner at 2 after being evacuated and filled, as is well known in theart, with a suitable gas, or mixture of gases such as argon, neon,helium, and mercury. The vessel or envelope 1 has a reentrant 80 stem 3provided with the press 4. This press supports a small glass tube 5(exaggerated in size in the drawing) which is enclosed at its outer endby a cylinder of insulating material which overhangs the end of theglass tube. This cylinder of insulating material may be made ofporcelain, isolantite, crowlite, or the like material. Isolantite is aheat treated clay product and crowlite is a heated and pressuretreatedproduct made of powdered oxides of metals. Fitting within the endof the insulating sleeve 6 is the cathode 7 made'in the form of a plugwhich is of tantalum or molybdenum in the best form. Extending from thestem tube 3 and formed integrally therewith is a hollow tube 8 lyingparallel to the central 95 axis of the envelope. Extending through thistube is a lead-in wire 11 which vconnects to a short length of platinumwire 10 sealed in the end thereof. Separated by the platinum wire 10 andencircling the insulating sleeve 6 at a short 100 distance from the endthereof is the anode or second electrode 9 inthe form of a ring. Thelead wire 12 passes through the press 4 and is connected to the cathode7 of the device. With a gas of suitable pressure within the envelope anda proper current excitation impressed across the leads 11 and 12 aluminous gas discharge is formed between the cathode and the anode upclose to the end wall of vessel 1. As is well known in this art, the endof the vessel is rounded in curs between curved anode wire 14 and thecath-` ode '1. It is important that the cylinderfy of insulatingmaterial 6 in both cases iit tightly over the glass tube 5 so that anelectrical discharge can never take place fromthe lead-in wires withinthe insulating cylinder 6. As is clear from the drawing the anode ring 9is very close to the exterior surface of the insulating sleeve but isactually out of contact therewith. In actual construction the'cathode iswithin one-eighth to three-sixteenths of the interior of the glassenvelope and the anode ring approximately onequarter of an inch from theforward end of the insulating sleeve 6. If desired large lead-in Wirescan be employed, particularly the wire 12, so as to properly conductaway the heat from the discharge which is generated at the cathodesurface. The lead-in wires, where they pass through the seals, will ofcourse conform to any standard practice whereby an airtight connectionis secured.

It has been found that tantalum and molybdenum are the best materialsfor the cathode. When tantalum is used there is no observable depositionupon or blackening of the glass envelope even after many hours ofconstant use, although when molybdenum is employed a slight blackeningdoes occur. However, either of the above metals are greatly superior toany other material commercially available for cathode construction. Inaddition the absorption of the gases contained in the envelope by thecathode is much less when tantalum is used than when ordinary metals,such as nickel, iron, and the like are employed. Platinum can beadvantageously employed as cathode material but the expense involvedwould be unnecessarily great.

From the foregoing disclosure it will be apparent that I have devised anew and novel construction in electron discharge devices which employscertain principles of construction and operation which may assume otherphysical forms than those disclosed in the drawing for purposes ofillustration. I do not, therefore, desire to be strictly limited to thedisclosure as given for purposes of illustration but rather to the scopeof the appended claims.

What I seek to secure by United States Letters Patent is:

1. In a gaseous discharge photographic sound recording device of thetype described, the combination comprising an envelope, a cathode withinsaid envelope, an insulating sleeve surrounding the cathode with theexception of the end surface thereof, and an anode supported adjacentthe exposed end surface of the cathode in close prox- ,lmity thereto.

2. In an electron discharge device of the type described, thecombination comprising an evacuated envelope, a cathode supported withinsaid envelope near one end thereof, an insulating sleeve encircling thecathode with the exception of the end surface thereof, and an anodesupported within said envelope, said anode being in the form of a ringencircling said insulating sleeve and lying below the plane of the endsurface of the cathode.

3. Ine-an electron discharge device of the type described, thecombination comprising an evacuated envelope, a cathode supported withinsaid envelope near .one end thereof, an insulating sleeve encircling thecathode with the exception of the end surface thereof, and an anodesupported within said envelope, said anode being in Athe form of a ringencircling said insulating sleeve and lying below the plane of the endsurface of the cathode, the end surface of said cathode being highlypolished.

4. In an electron discharge device of the type described, thecombination comprising an envelope having a rounded end surface, aninsulating tube supported within said envelope, an insulating sleeveencircling said tube, a cathode lying within said insulating sleeve withthe end surface exposed, a lead wire for said cathode passing throughthe tube, a hollow support within said envelope, an anode supportedtherefrom and encircling said sleeve, and a lead wire insulated throughsaid hollow support and connected to said anode.

5. In an electron discharge device of the type described, thecombination comprising an en-l velope having a rounded end surface, aninsulating tube supported within said envelope, an insulating sleeveencircling said tube, a cathode lying within said insulating sleeve withthe end surface exposed, a lead wire for said cathode passing throughthe tube, a hollow support within said envelope, an anode supportedtherefrom and encircling said sleeve, and a lead wire insulated throughsaid hollow support and connected to said anode, said anode lying in aplane below the end surface of the cathode.

6. In an electron discharge device of the type described, thecombination comprising an envelope having a rounded end surface, aninsulating tube supported within said envelope, an insulating sleeveencircling said tube. a cathode 1Z0 lying within said insulating sleevewith the end surface exposed, a lead wire for said cathode passingthrough the tube, a hollow support within said envelope, an anodesupported therefrom and encircling said sleeve, and a lead wireinsulated through said .hollow support and connected to said anode, saidanode lying in a plane below the end surface of the cathode, the endsurface of said cathode beinghighly polished.

7. In an electron discharge sound recording de- 'll' vice of the typedescribed, the combination comprising an evacuated vessel, an insulatedcathode of tantalum having its end surface only exposed, and an anodesupported very close to the exposed end of said cathode and insulatedtherefrom.

8. vA gaseous discharge device for photographically recordingfluctuating voice currents, comprising an evacuated vessel having aspherical end wall, a cathode within said vessel having its end 14.surface very close to the spherical end wall of b the vessel, an anodeadjacent the cathode, and meas for restricting the glow discharge to theend of the cathode adjacent the spherical end wall of the vessel. M.

LEE nl: FOREST.

